Process for separating potassium compound from brines



OFF-ICE,

HARRY W. MORSE, OF TBONA, CALIFORNIA, ASSIG'NOR TO AMERICAN TRONA CORPO- RATION, OF TBONA, CALIFORNIA,

A conr'om'rron OF DELAWARE.

PROCESS FOR, SEPARATING POTASSIUM COMPOUND FROM BBINES.

following is a specification.

This invention relates to separation of a potassium salt from solutions containing the same, together with other salts, and particularly to separation of potassium chlorid from brines, brine-residues, or mother liquors, containing potassium chlorid and borax as important constituents, and resulting, for example, from the treatment of Searles Lake or similar brines for the recovery of potassium compqunds. In this treatment, after the remova'mf the major portion of the sodium chlori and of some of the other salts present, there remains a solution'consisting largely of potassium chlorid and contains borax, and the main object of the present invention is to separate the potassium chlorid substantially free from borax, from sucha solution.

The composition of the hot liquor obtained by evaporation and treatment of Searles Lake brinesfrom'which much of the sodium chlorid and other salts have been removed by such treatment may be stated as approximately Potassium chlorid 16% Borax 7 Sodium chlorid 10 Sodium carbonate- 8 Sodium sulfate 2 Total solids 437 The presence of such a considerable proportion of borax, as Well as sodium chlorid in the product obtained from this solution, detracts from its value as a fertilizer or for other purposes. The potassium chlorid may be obtained comparatively free from sodium chlorid .by cooling and crystalhzmg operations, but the salt so obtained generally still objectionable amount of borax, which under ordinary conditions of cooling tends to separate out to about the same extent, relatively speaking, as the potassium. chlorid. v

I have found that by very rapidly cool ng Specification of Letters Patent.-

solution during moving the mother li the solution, the potassium chlorid may be caused to separate from the solution, withinvention is based on this fact. My invention may be carried out as fol lows: The solution coming from the preout substantial admixture of borax, and my' Patented June 15,1920; e, 1918. Serial no. 264,339.

liminary concentrating, and separating operations for the removal of common salt,

and other salts, and having, about the composition above stated and a temperature of 90 to 95 C. is passed throu h cooling aparatus of any type adapted or rapid 0001- mg, for example, tanks containing pipes through which coolin liquid is caused to circulate, and is there y'rapidly cooled to about 30 to 35 C., the cooling bein effected in, say, from one to two hours. nder these conditions, the potassium chlorid crystallizes substantially free from borax (which is impossible with slow cooling), so that the resulting crystallized salt, after draining away the mother liquor, contains about 7 5 KCl, about 10% of moisture and about 2.5%, borax. By centrifugal removal oi. the mother liquor from the salt, the

moisture content may be reduced to say, 3.5% and the borax contentto about .8%,

the borax present being substantially limited to what is in solution in the mother liquor adhering to the salt. A still lower borax content may be obtained by washing with cold water, thus displacin adhering mother liquor from the-salts. he mother liquor from which potassium compound has been recovered to the required extent by this process may then be treated in any suitable manner for recovery of other salts, for examfile, borax. v

y invention depends on the selective eflect of rapid coolin in separating potassium chlorid in pre erenoe to borax, the time element being the controlling factor in the selective action. It is therefore of the essence ofmy invention that the solution be cooled with suflicientrapidity to cause the required amount of potassium chlorid to crystallize, without separation in solid form of any substantial amount of borax. Thethe cooling is in a conditionof supersaturation with respect to borax, but by cooling rapidly, as stated, to cause crystallization of potassium chlorid and reuor from the potas vloo sium chlorid crystals efore the borax has time to crystallize, I prevent crystallization of any borax in solid form and obtain sub-' stantially pure potassium chlorid.

What I claim is:

1. The process of separating potassium chlorid from solutions containing the same,

together with borax, which consists in subjecting such solution to sufliciently rapid cooling action to separatepotassium chlorid without separation of borax in solid form.

2. The process of separating potassium chlorid from solutions containing the same,

together with borax, which consists in reducing the temperature of such solution from about 90 C. to about 30 C. in less than two hours, thereby causing potassium chlorid to crystallize free from soli borax, and separating the crystallized salt from the mother liquor.

In testimony whereof I have hereunto subscribed my name this 16th dayof November, 1918.

HARRY WQMORsE. 

